Orthodontics is the practice of manipulating a subject's teeth to provide better function and appearance. In general, brackets are bonded to a subject's teeth and coupled together with an arched wire. The combination of the brackets and wire provides a force on the teeth causing them to move. Once the teeth have moved to a desired location and are held in place for a certain period of time, the body adapts bone and tissue to maintain the teeth in the desired location. A subject may be fitted with a retainer to help keep the teeth in the desired location.
Orthodontists initially base their treatment on a mental image of the subject's physical orthodontic structure and a mental image of a desired physical orthodontic structure for the subject, which may be assisted by x-rays and/or models. Based on these mental images, the orthodontist relies on his/her expertise to place the brackets and/or bands on the teeth and to manually bend (i.e., shape) wire, such that a force is asserted on the teeth to reposition them into the desired physical orthodontic structure. As the teeth move towards the desired location, the orthodontist makes continual judgments as to the progress of the treatment, the next step in the treatment (e.g., new bend in the wire, reposition or replace brackets, head gear, etc.), and the success of the previous step.
In general, an orthodontist makes manual adjustments to the wire and/or replaces or repositions brackets based on his or her expert opinion. Unfortunately, in the oral environment, it is difficult for a human being to accurately develop a visual three-dimensional image of an orthodontic structure due to the limitations of human sight and the physical structure of a human mouth. In addition, it is difficult (if not impossible) to accurately estimate three-dimensional wire bends (with accuracy within a few degrees) and to manually apply such bends to a wire. Further, it is difficult (or impossible) to determine an ideal bracket location to achieve the desired orthodontic structure based on the mental images. It is also extremely difficult to manually place brackets in what is estimated to be the ideal location. Accordingly, orthodontic treatment is an iterative process requiring multiple wire changes, with the success and speed of the process being dependent on the orthodontist's motor skills and diagnostic expertise. As a result of multiple wire changes, cost and subject discomfort is increased. The quality of care may also vary greatly from orthodontist to orthodontist, as does the time to treat a subject.
The practice of orthodontics relies heavily on the expert opinions and judgments of the orthodontist. Many innovations have been developed to aid orthodontists and other medical professionals attempting to align teeth. For example, U.S. Pat. No. 5,518,397 to Andreiko, et. al. provides a method of forming an orthodontic brace. The method includes obtaining a model of a subject's teeth and a prescription of desired positioning of the teeth. The contour of the subject's teeth is determined from the model. Calculations of the contour and the desired positioning of the subject's teeth are made and custom brackets are then created for receiving an arch wire to form an orthodontic brace system. The device of U.S. Pat. No. 5,518,397 places an arched wire on the bracket in a progressive curvature in a horizontal plane and a substantially linear configuration in a vertical plane. The brackets are customized to provide three-dimensional movement of the teeth. U.S. Pat. No. 5,518,397 to Andreiko, et. al., and all of the patents and references referred to in this specification, are hereafter incorporated by reference in their entirety.
Other innovations relating to bracket and bracket placements have also been patented. For example, such patent innovations are disclosed in U.S. Pat. No. 5,618,716 entitled “Orthodontic Bracket and Ligature” (a method of ligating arch wires to brackets), U.S. Pat. No. 5,011,405 “Entitled Method for Determining Orthodontic Bracket Placement,” U.S. Pat. No. 5,395,238 entitled “Method of Forming Orthodontic Brace,” and U.S. Pat. No. 5,533,895 entitled “Orthodontic Appliance and Group Standardize Brackets therefore and methods of making, assembling and using appliance to straighten teeth.”
Kuroda et al. (1996) Am. J. Orthodontics 110:365-369 describes a method for laser scanning a plaster dental cast to produce a digital image of the cast. See also U.S. Pat. No. 5,605,459, and U.S. Pat. Nos. 5,533,895; 5,474,448; 5,454,717; 5,447,432; 5,431,562; 5,395,238; 5,368,478; and 5,139,419, assigned to Ormco Corporation, describing methods for manipulating digital images of teeth for designing orthodontic appliances.
U.S. Pat. No. 5,011,405 describes a method for digitally imaging a tooth and determining optimum bracket positioning for orthodontic treatment. Laser scanning of a molded tooth to produce a three-dimensional model is described in U.S. Pat. No. 5,338,198, and U.S. Pat. No. 5,452,219 describes a method for laser scanning a tooth model and milling a tooth mold. Digital computer manipulation of tooth contours is described in U.S. Pat. Nos. 5,607,305 and 5,587,912. Computerized digital imaging of the arch is described in U.S. Pat. Nos. 5,342,202 and 5,340,309.
Other patents of interest include U.S. Pat. Nos. 5,549,476; 5,382,164; 5,273,429; 4,936,862; 3,860,803; 3,660,900; 5,645,421; 5,055,039; 4,798,534; 4,856,991; 5,035,613; 5,059,118; 5,186,623; and 4,755,139.
Realistic simulations of teeth position are extremely helpful to many orthodontic treatment processes. Orthodontists may use plaster models of the upper and lower arch, to create a set-up that may be manipulated to model the starting and finishing positions of teeth. Thus, the teeth may be modeled to help eliminate guesswork. Brackets may be bonded to each tooth model to show the orthodontist the geometry of the wire to run through the bracket slots to achieve a desired result. The bracket position may then be transferred to the original malocclusion model. To make sure that the brackets will be bonded at exactly this position at the real subject's teeth, small templates for every tooth can be fabricated that fit over the bracket and a relevant part of the tooth and allow for reliable placement of the bracket on the subject's teeth. Alternatively, a transfer tray may be fabricated for each arch by placing each single bracket onto a model of the malocclusion and then fabricating a single transfer tray per arch that covers all brackets and relevant portions of every tooth. Thus, a transfer tray may help assure a very quick and yet precise bonding using indirect bonding.
U.S. Pat. No. 5,431,562 to Andreiko et al. describes a computerized, appliance-driven approach to orthodontics in which shape information of teeth is acquired and a target archform is calculated from the shape information. The shape of customized bracket slots, the bracket base, and the shape of the orthodontic archwire, are calculated in accordance with a mathematically-derived target archform. However, the orthodontist does not substantially interact with the appliance design.
Align Technologies also offers transparent, removable aligning devices. In this system, an orthodontist obtains an impression model of a subject's dentition and ships this model to a remote appliance manufacturing center, where it is scanned with a CT scanner. A computer model of the dentition in a final target situation is generated at the appliance manufacturing center and made available for viewing to the orthodontist over the Internet. The orthodontist indicates changes he or she wishes to make to individual tooth positions. Later, another virtual model is provided over the Internet and the orthodontist may review the revised model, and indicates any further changes. After several such iterations, the target situation is agreed upon. A series of removable aligning devices (or shells) are then manufactured and delivered to the orthodontist. The shells, in theory, will move the subject's teeth to the desired or (final) target position.
The coordination of the different steps of the treatment (the overall treatment process) typically involves early input from the practitioner (e.g., doctor, dental technician, etc.) in forming the aligner design referencing only the initial dental alignment of the subject. Most treatment processes do dynamically react to the ongoing treatment of the patent by the dental aligner. Thus, it may be difficult to optimize the interaction between the practitioner and the ongoing aligners produced.
U.S. Pat. No. 6,699,037 by Align Technology describes improved methods and systems for repositioning teeth from an initial tooth arrangement to a final tooth arrangement. Repositioning is accomplished with a system comprising a series of appliances configured to receive the teeth in a cavity and incrementally reposition individual teeth in a series of at least three successive steps. The individual appliances preferably comprise a polymeric shell having the teeth-receiving cavity formed therein, typically by stereo lithographic molding. Each individual appliance is configured so that its tooth-receiving cavity has a geometry corresponding to an intermediate or end tooth arrangement intended for that appliance. That is, when an appliance is first worn by the subject, certain of the teeth will be misaligned relative to an undeformed geometry of the appliance cavity. The appliance, however, is sufficiently resilient to accommodate or conform to the misaligned teeth, and will apply sufficient resilient force against such misaligned teeth in order to reposition the teeth to the intermediate or end arrangement desired for that treatment step.
U.S. Pat. Nos. 6,471,511 and 6,682,346 describe Align Technology's stereo lithographic fabrication process. Several drawbacks exist however with the stereo lithography process. The materials used by stereo lithography processes may be toxic and harmful to human health. Stereo lithography builds the aligner layer by layer, which may create spaces susceptible to the growth of germs and bacteria when it is worn by a subject. Furthermore, Align Technology's stereo lithography process also requires a different aligner mold at each stage of the treatment, which produces a lot of waste and is environmental unfriendly. Thus, there is a need for practical, effective and efficient methods to produce a dental aligner.
Modeling a subject's teeth, such as modeling the upper or lower dental arches (including the manner in which the teeth interact) may be an important feature in using and creating an alignment device. A model of the subject's teeth can help guide the desired movement of the subject's teeth during an orthodontic treatment. The model can help avoid interference between a subject's teeth when undergoing dental re-alignment. A model can also provide input for the design and manufacturing of dental aligner devices. Thus, there is a need to accurately and efficiently obtain models of subjects' dental arches, including both virtual and actual models.
Another challenge for orthodontic treatment using aligning devices is to accurately translate the subject's teeth movement into treatment measures in the iterative treatment progress. The current treatment techniques are not able to quantitatively monitor the teeth movement of the subject's teeth and precisely adjust the treatment in accordance to the teeth movement of the subject's teeth.
Another challenge for orthodontic treatment using removable aligning devices is to accurately and most effectively render teeth movement. The current treatment techniques are often unable to account for the real and least resistance movement of the subject's teeth, which results in wanted teeth movement and/or unnecessary number of treatment steps.
By tracking the relative positions of the teeth in the upper and lower arches, dental aligner devices can be designed and fabricated to reflect the ongoing treatment by an orthodontist or user, as well as the effect of the treatment on the subject. This may ultimately save in cost, treatment time, and may also enhance user comfort.
Finally, the dental treatment processes may be designed to allow modification of the treatment steps based on the movement of the subject's teeth. Furthermore, there is a need for more optimal treatment processes, including the manufacturing of the dental aligners. Described herein are devices, systems, and methods which may address some of the problems described above.